Thunderbird has a built in feature called Junk Mail. It automatically detects incoming email messages that appear to be junk mail (also known as spam), and then can perform a number of configurable actions on those messages. Messages that Thunderbird thinks are junk will display a junk mail icon.
At first, you must train Thunderbird to identify junk mail by using the Junk toolbar button to mark messages as Junk or Not Junk. Once Thunderbird is correctly identifying junk mail, you can use the Junk Mail Controls to automatically move incoming junk mail to a folder.
Junk Mail Controls
- Open Thunderbird.
- Click on Tools > Junk Mail Controls… > Enable junk mail controls. This will cause Thunderbird to automatically classify the junk status of any incoming messages.
- After clicking on the option to Move incoming messages determined to be junk mail to:, select a folder for the junk mail to be automatically moved into.
- Click on the OK button to save your changes.
Note: From time to time, it would be a good idea to check the folder that you set up as your junk mail folder. Thunderbird may wrongly classify legitimate mail as junk, and will them move these “false positives” to the junk mail folder.